Piezoelectric array using parallel connected elements to form groups which groups are ≈1/2λ in width

Abstract

In an exemplary embodiment a transducer comb for an ultrasonic array or a compound scanner consists of a specifiable number of transducer elements joined together in a specific area formation, the width of each transducer element being smaller than its height. In the case of sonic heads of this type, given an optimum radiation or receiving power, respectively, the lateral resolution is to be significantly improved. This is achieved by a transducer element arrangement comprising a fine subsidivision of the transducer elements in such a manner that the width of each individual transducer element lies markedly below half the wavelength (λ/2) of the radiated, or received, ultrasonic waves, whereby, however, within the arrangement, in each instance, always a specified number of transducer elements of the fine subdivision is combined into a group through parallel-connection. The total radiation/receiving surface, including the intermediate spaces, of such a group is to correspond to at least approximately the active area of an individual element of conventional transducer element arrangements. In spite of a relatively high loss due to the fine division of the transducer, at least the same radiation efficiency as in the case of conventional transducer arrangements results with the group interconnection, whereby, however, the echo response is virtually free of transverse vibrations.

We claim as our invention: 
     
       1. An ultrasonic head, especially for operation as an ultrasonic array or a compound scanner, comprising a specifiable number of transducer elements joined together in a specific surface configuration, the width of each transducer element being smaller than the height, characterized by a transducer element arrangement (9) with a fine subdivision of the transducer elements (11a, 12a through 11n, 12n; 21a through 21n; 22a through 22n; 24a through 24n) in such a manner that the width (b) of each individual transducer element, at least at one location, lies substantially below half the wavelength (λ/2) of the radiated, or received ultrasonic waves, the transducer element arrangement (9), in each instance, having successive sets of the transducer elements of the fine subdivision electrically combined into respective groups (13) through electrical parallel-connection; the total radiation or receiving active surface including the intermediate spaces (20) of each of said groups having a width equal to at least about one-half the wavelength (λ/2), each set of transducer elements comprising at least two of said transducer elements and having electrical conductors (14, 16; 25) directly and permanently interconnecting said set of transducer elements for joint transducing operation. 
     
     
       2. An ultrasonic head according to claim 1, characterized in that the width (b) of each individual transducer element of a group (13) is at least less than λ/4. 
     
     
       3. An ultrasonic head according to claim 1, characterized in that the intermediate spaces manifest gap widths (s) on the order of magnitude of a maximum of 1/5 of the respective transducer element width (b). 
     
     
       4. An ultrasonic head according to claim 1, characterized in that the parallel connection into groups (13) occurs by means of common group-contacting (14, 16; 25) of the individual transducer elements within the group. 
     
     
       5. An ultrasonic head according to claim 4, characterized in that there is allocated to each group-contacting (14, 16; 25) a separate signal line (18, 19) for the purpose of operating the group (13). 
     
     
       6. Ultrasonic head according to claim 1, with the transducer groups (13) being formed of rod shaped transducer elements (11a, 12a through 11n, 12n) each having a width (b) which is constant over the element length (l) and having an element height (h), and having a width (b) which is smaller than one-half the wavelength (λ/2). 
     
     
       7. An ultrasonic head according to claim 1, with the transducer groups being formed of transducer elements (21a through 21n) with a constant element height (h), but with a width (b) increasing over the element length (l) from a low value which is smaller than λ/2 to a maximum value which maximum value lies in the range of at least about λ/2. 
     
     
       8. An ultrasonic head according to claim 1, with the transducer element groups being formed of transducer elements (22a through 22n) with a constant element length (l), and a width (b) increasing over the element height (h) from a low value smaller than λ/2 to a maximum value which maximum value lies in the range of at least about λ/2. 
     
     
       9. An ultrasonic head according to claim 1, with the transducer element groups having a length less than the length of the total active surface to provide a subdivided surface arrangement with longitudinal and transverse gaps between the groups. 
     
     
       10. An ultrasonic head according to claim 1, characterized by the transducer element groups being arranged to define a round transducer active surface.